The present disclosure relates to congestion management, and more specifically, to hierarchical occupancy based congestion management.
Server farms, also known as data centers, are becoming more and more utilized. Without proper congestion management, the increased network utilization will reduce the performance of applications that utilize these networks. Many data centers are using Converged Enhanced Ethernet (CEE) that allows high link speeds and short delays while introducing lossless operation beyond the lossy operation provided by traditional Ethernet.
Lossless CEE operation requires a distributed congestion management system with congestion detection at congestion points. In response to detecting congestion, the congestion points send congestion notification messages to traffic sources, which instruct the traffic sources to reduce their data transmission rate. Current congestion management schemes and congestion notification schemes are explicit arrival rate congestion samplers that are triggered by new arrivals.
Congestion points include a buffer, typically assumed to be a FIFO queue, which acts as a rate mismatch integrator. The congestion level of the buffer is determined by packet arrivals and the service times of the packets leading to departures. The buffer accumulates the difference between the arrivals and the departures of the aggregate flow. Once the congestion point determines that there is congestion in the buffer, the congestion point randomly samples arriving packets and sends congestion notification messages to the traffic sources of the sampled packets.
Accordingly, a data flow with a higher arrival rate at the congestion point is likely to be sampled more often than one with a lower arrival rate. The congestion management system throttles the transmission rate of the data flows having higher arrival rates to the congestion point more than data flows having lower arrival rates. However, the arrival rate of a data flow is not necessarily indicative of its relative contribution to the congestion.